A Security Intercom System is a stand-alone voice or video communications system for use within a building or small collection of buildings, functioning independently of the public telephone network. Sometimes Security Intercom System is called talkback or doorphone. Security Intercom Systems are generally mounted permanently in buildings and vehicles. Security Intercom Systems can incorporate connections to public address loudspeaker systems, walkie talkies, telephones, and to other intercom systems. Some Security Intercom Systems incorporate control of devices such as signal lights and door latches.